1. Field of the Invention
The present invention relates to a drive torque estimation device for a compressor which estimates a drive torque of a compressor used in a refrigerating cycle of a vehicle-use air conditioning unit mounted on a vehicle, and a condenser used for the device.
2. Description of the Related Art
The estimation with high accuracy of a torque of a compressor in a refrigerating cycle which exhibits large power consumption among vehicle-mounted auxiliary devices is an important task for reducing a fuel consumption amount of a vehicle.
As also shown in FIG. 6, a torque of a compressor can be estimated using a general formula expressed by the following formula 1, for example. Pd indicates a measured value of a discharge pressure of the compressor, and Ps indicates a measured value of a suction pressure of the compressor. Compressor total efficiency which is a variable parameter can be introduced from Pd, and a specific volume can be introduced from Ps. Further, a flow rate of a refrigerant G can be calculated by detecting the difference between a pressure C1 on an upstream side of a position in a refrigerating cycle where flow passage resistance is present and a pressure C2 on a downstream side of the position where flow passage resistance is present. A unit matching coefficient is provided for converting a mass flow rate into a volume flow rate, and is a constant.Torque estimated value (N·m)=Ps×G×(Pd/Ps)n/total efficiency of compressor×specific volume×unit matching coefficient
Accordingly, variable parameters other than the refrigerant flow rate can be accurately grasped based on a measured values of the discharge pressure Pd and the suction pressure Ps of the compressor and hence, the accuracy of the torque estimated value of the compressor depends on the accuracy of measurement of a refrigerant flow rate G, that is, depends on how accurately the pressure difference (C1−C2) between the pressure on the upstream side of the position where the flow passage resistance is present and the pressure on the downstream side of the position can be measured.
In view of the above, in the related art, as a technique for measuring the refrigerant flow rate G in the refrigerating cycle (the technique for detecting the pressure difference between the pressure on the upstream side of the position where the flow passage resistance is present and the pressure on the downstream side of the position), there has been known a technique as described in JP-A-2011-33235 (patent literature 1) where an orifice is mounted in the inside of a refrigerant circuit and a pressure sensor is provided in front of and behind the orifice for detecting the pressure difference, and there has been also known a technique as described in Japanese Patent No. 4119143 (patent literature 2) where a condenser is used as a resistive element, a condenser pressure difference detection means which detects the pressure difference between an inlet-side refrigerant pressure and an outlet-side refrigerant pressure of the condenser is provided, and a flow rate of a refrigerant which flows through the condenser is calculated based on a detection value obtained by the condenser pressure difference detection means.